[serde_bencode] Impl int

src/serde_bencode.rs

@@ -1,6 +1,5 @@
 use std::fmt;
 use std::fmt::Display;
-use std::ops::{AddAssign, MulAssign};
 
 use serde::{de, Deserialize, ser};
 use serde::de::Visitor;
@@ -14,6 +13,7 @@ pub enum Error {
     Eof,
     Syntax,
     ExpectedInteger,
+    ExpectedIntegerEnd,
     ExpectedListEnd,
     ExpectedDictEnd,
     TrailingCharacters,
@@ -38,6 +38,7 @@ impl Display for Error {
             Error::Eof => formatter.write_str("unexpected end of input"),
             Error::Syntax => formatter.write_str("syntax error"),
             Error::ExpectedInteger => formatter.write_str("expected integer"),
+            Error::ExpectedIntegerEnd => formatter.write_str("expected integer end char 'e'"),
             Error::ExpectedListEnd => formatter.write_str("expected list end char 'e'"),
             Error::ExpectedDictEnd => formatter.write_str("expected dict end char 'e'"),
             Error::TrailingCharacters => formatter.write_str("trailing characters")
@@ -79,12 +80,25 @@ impl<'de> Deserializer<'de> {
         }
     }
 
+    fn next_byte(&mut self) -> Result<u8> {
+        let ch = self.peek_byte()?;
+        self.input = &self.input[1..];
+        Ok(ch)
+    }
+
     fn parse_int<T>(&mut self) -> Result<T>
     where
-        //T: AddAssign<T> + MulAssign<T> + From<i8>,
-        T:  From<i8>,
+        T:  From<i8> + std::str::FromStr,
     {
-        Ok(42.into())
+        if self.next_byte()? != 'i' as u8 {
+            return Err(Error::Syntax)
+        }
+        let end_pos = self.input.iter().position(|&x| x == 'e' as u8)
+            .ok_or_else(|| Error::ExpectedIntegerEnd)?;
+        let int_str = std::str::from_utf8(&self.input[..end_pos]).map_err(|_| Error::Syntax)?;
+        let int = int_str.parse::<T>().map_err(|_| Error::ExpectedInteger)?;
+        self.input = &self.input[end_pos + 1..];
+        Ok(int)
     }
 }
 
@@ -304,11 +318,13 @@ impl <'de, 'a> de::Deserializer<'de> for &'a mut Deserializer<'de> {
 
 #[cfg(test)]
 mod test {
-    use crate::serde_bencode::from_bytes;
+    use crate::serde_bencode::{Error, from_bytes};
 
     #[test]
     fn test_int() {
         assert_eq!(from_bytes(&"i42e".as_bytes()), Ok(42));
+        assert_eq!(from_bytes::<i32>(&"i42".as_bytes()), Err(Error::ExpectedIntegerEnd));
+        assert_eq!(from_bytes::<i32>(&"42e".as_bytes()), Err(Error::Syntax));
         // 2**16 + 1 = 65537
         assert_eq!(from_bytes(&"i65537e".as_bytes()), Ok(65537));
     }